Truly fast oils are in the 7-10 second range, while medium speed are 11-14 second. Park Metallurgical/Heatbath #50 is 7-10, Park Metallurgical/Heatbath AAA is 11-14 second. The McMaster oil would be more like Houghton quench “G” which is 11-14 second. Houghton makes a type “K” that is faster and more like the #50.
Normally the 11-14 second oils would be too slow for 10XX like 1084, but I would ask how think are your knives? If they are typically 3/16” or less at the spine you may be able to get away with the McMaster Carr oil. What you will get when the oil can’t quite meet the speed requirements of the steel is increasing amounts of pearlite as the cross section increases. So, your edge will be mostly martensitic and you will get increasing amounts of pearlite as you move towards the spine, and when the pearlite becomes predominant you will start to form auto-hamon features.
So, if you are very fussy about complete, thorough and consistent, results then you will be bothered if you don’t have complete martensite transformation in the blade body and spine. But many folks have no problem with only the first 3/8” of the edge side being fully hardened, as is evident by the ubiquitous nature of hamons on knives these days.
It is worth noting, however, that if you are intentionally going for hamon, you will want the fast oil as the clay moves the cooling curves significantly.